1. Field of the Invention
The invention relates to a thin film magnetic head including at least an inductive magnetic transducer for use in recording, and a magnetic recording apparatus equipped with the thin film magnetic head.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in an areal recording density of a magnetic recording medium (hereinafter simply referred to as “a recording medium”), such as a hard disk. As recording modes of the thin film magnetic head, known are, for example, a longitudinal recording mode which involves orienting a signal magnetic field in the in-plane direction of the recording medium (i.e., the longitudinal direction thereof), and a perpendicular recording mode which involves orienting a signal magnetic field in a direction perpendicular to a surface of the recording medium. Although the longitudinal recording mode is widely used at present, the perpendicular recording mode rather than the longitudinal recording mode can be regarded as promising in the future, allowing for market trends incident to an increase in the areal recording density. The reason is as follows. The perpendicular recording mode has not only the capability of ensuring a high linear recording density, but also the advantage that the recording medium having information recorded thereon is resistant to thermal fluctuations.
For instance, the thin film magnetic head of the perpendicular recording mode includes a thin film coil which generates a magnetic flux for use in recording, a magnetic pole layer which emits the magnetic flux generated by the thin film coil to the recording medium, and a write shield layer which prevents divergence of the magnetic flux emitted from the magnetic pole layer. As this type of thin film magnetic head, there is known, for example, the thin film magnetic head including the magnetic pole layer and the write shield layer disposed on the trailing side with respect to the magnetic pole layer (see, e.g., Japanese Unexamined Patent Application No. 2001-250204 and European Patent Application No. 0360978). The thin film magnetic heads disclosed in these patent literatures have the advantage of increasing the recording density because of the presence of the write shield layer which prevents the magnetic flux from diverging during recording and thus reduces a write track width on the recording medium.
To improve the reliability of the thin film magnetic head of the perpendicular recording mode, it is necessary to ensure the magnetic operating characteristics of the thin film magnetic head with stability. However, the conventional thin film magnetic heads have the following problem: when an undesired magnetic field (i.e., a stray external magnetic field) is generated from an external magnetic field source such as a voice coil motor, unintentional writing (i.e., overwriting) may take place and result in unintentional erasing of information recorded on the recording medium, depending on the effect of the stray external magnetic field, during non-recording, more specifically in state where a current for use in recording is not fed through the thin film coil. To ensure the magnetic operating characteristics of the thin film magnetic head of the perpendicular recording mode with stability, an urgent necessity is to establish a technique for minimizing the above-mentioned unintentional erasing of information during non-recording.